Western Avocado Leafroller

Western avocado leafroller (family Tortricidae), is primarily a pest of avocado. It occurs in most California groves and occasionally increases dramatically, causing severe fruit damage. This caterpillar also damages citrus, where it is called amorbia, its official common name. Amorbia is often called just "leafroller." However, amorbia, avocado looper, and orange tortrix all roll avocado leaves and web plant parts together with silk.

Amorbia (and orange tortrix) adults are bell-shaped when their wings are folded at rest. Their variably colored forewings are typically orangish to tan with dark markings. Adult amorbia are about 1 inch (2.5 cm) long, about twice the size of orange tortrix adults.

Each amorbia female lays about 150 to 200 eggs during her 2 to 3 week life. These light green, oval-shaped eggs occur mostly on the upper side of leaves close to the midrib. Amorbia (and orange tortrix) eggs are laid overlapping or shinglelike in a flat mass. Amorbia lays about 5 to 100 eggs per mass, with an average of 25 eggs per mass. Eggs darken and larvae emerge about 2 weeks after oviposition. Hatched egg masses resemble whitish patches on leaves.

Amorbia larvae develop through five instars. At maturity they are 0.75 to 1 inch long. Caterpillars are yellowish green when young, and mostly darker green when mature. Older larvae have one short dark horizontal line on their side on their thorax just behind the head and above the first pair of legs. Other avocado caterpillars lack these distinct black marks. Amorbia feed in nests of leaves and fruit tied together with silk. When disturbed, amorbia and orange tortrix larvae often wriggle violently and drop to the ground.

Amorbia pupate for 2 to 3 weeks in rolled leaves. The 0.5 to 0.75 inch long pupae initially are pale green, gradually turn tan, and become brown when mature.

Egg to adult development time is about 1.5 months at an average temperature of 75°F. Amorbia typically has three generations per year at warmer growing areas. From inland Ventura to San Diego Counties, most adults fly and females oviposit during January through April, May through June, and during September through October. Two generations a year occur on average in coastal groves. In Santa Barbara County most moths emerge and lay eggs during March through June, and August through November.